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Add logic to drop the priority of the page fill task

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git-svn-id: svn://svn.code.sf.net/p/nuttx/code/trunk@2857 42af7a65-404d-4744-a932-0658087f49c3
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patacongo 2010-08-15 16:50:25 +00:00
parent b12fa96569
commit f9060631fc
1 changed files with 12 additions and 12 deletions
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24
Documentation/NuttXDemandPaging.html
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@ -160,7 +160,7 @@
<dl>
<dt><code>g_waitingforfill</code></dt>
<dd>An OS list that is used to hold the TCBs of tasks that are waiting for a page fill.</dd>
<dt><code>g_pendingfilltcb</code></dt>
<dt><code>g_pftcb</code></dt>
<dd>A variable that holds a reference to the TCB of the thread that is currently be re-filled.</dd>
<dt><code>g_pgworker</code></dt>
<dd>The <i>process</i> ID of of the thread that will perform the page fills.</dd>
@ -307,8 +307,8 @@
</p>
<p>
The page fill worker thread will maintain a static variable called <code>_TCB *g_pendingfilltcb</code>.
If no fill is in progress, <code>g_pendingfilltcb</code> will be NULL.
The page fill worker thread will maintain a static variable called <code>_TCB *g_pftcb</code>.
If no fill is in progress, <code>g_pftcb</code> will be NULL.
Otherwise, it will point to the TCB of the task which is receiving the fill that is in progess.
</p>
<ul><small>
@ -319,7 +319,7 @@
</small></ul>
<p>
When awakened from <code>pg_miss()</code>, no fill will be in progress and <code>g_pendingfilltcb</code> will be NULL.
When awakened from <code>pg_miss()</code>, no fill will be in progress and <code>g_pftcb</code> will be NULL.
In this case, the page fill worker thread will call <code>pg_startfill()</code>.
That function will perform the following operations:
<ul>
@ -387,10 +387,10 @@
In this non-blocking case, the callback <code>pg_callback()</code> will perform the following operations when it is notified that the fill has completed:
<ul>
<li>
Verify that <code>g_pendingfilltcb</code> is non-NULL.
Verify that <code>g_pftcb</code> is non-NULL.
</li>
<li>
Find the higher priority between the task waiting for the fill to complete in <code>g_pendingfilltcb</code> and the task waiting at the head of the <code>g_waitingforfill</code> list.
Find the higher priority between the task waiting for the fill to complete in <code>g_pftcb</code> and the task waiting at the head of the <code>g_waitingforfill</code> list.
That will be the priority of he highest priority task waiting for a fill.
</li>
<li>
@ -409,20 +409,20 @@
<a name="TaskResumption"><h2>Task Resumption</h2></a>
<p>
For the non-blocking <code>up_fillpage()</code>, the page fill worker thread will detect that the page fill is complete when it is awakened with <code>g_pendingfilltcb</code> non-NULL and fill completion status from <code>pg_callback</code>.
For the non-blocking <code>up_fillpage()</code>, the page fill worker thread will detect that the page fill is complete when it is awakened with <code>g_pftcb</code> non-NULL and fill completion status from <code>pg_callback</code>.
In the non-blocking case, the page fill worker thread will know that the page fill is complete when <code>up_fillpage()</code> returns.
</p>
<p>
In this either, the page fill worker thread will:
<ul>
<li>
Verify consistency of state information and <code>g_pendingfilltcb</code>.
Verify consistency of state information and <code>g_pftcb</code>.
</li>
<li>
Verify that the page fill completed successfully, and if so,
</li>
<li>
Call <code>up_unblocktask(g_pendingfilltcb)</code> to make the task that just received the fill ready-to-run.
Call <code>up_unblocktask(g_pftcb)</code> to make the task that just received the fill ready-to-run.
</li>
<li>
Check if the <code>g_waitingforfill</code> list is empty.
@ -432,10 +432,10 @@
Remove the highest priority task waiting for a page fill from <code>g_waitingforfill</code>,
</li>
<li>
Save the task's TCB in <code>g_pendingfilltcb</code>,
Save the task's TCB in <code>g_pftcb</code>,
</li>
<li>
If the priority of the thread in <code>g_pendingfilltcb</code>, is higher in priority than the default priority of the page fill worker thread, then set the priority of the page fill worker thread to that priority.
If the priority of the thread in <code>g_pftcb</code>, is higher in priority than the default priority of the page fill worker thread, then set the priority of the page fill worker thread to that priority.
</li>
<li>
Call <code>pg_startfill()</code> which will start the next fill (as described above).
@ -446,7 +446,7 @@
Otherwise,
<ul>
<li>
Set <code>g_pendingfilltcb</code> to NULL.
Set <code>g_pftcb</code> to NULL.
</li>
<li>
Restore the default priority of the page fill worker thread.